Conventionally, some steam generators have heat dissipation fins which define a labyrinthine passage in the steam generating chamber (for example, see Patent Literature 1). Providing the heat dissipation fins in this way can prevent boiling water from running-up from a bottom of the steam generating chamber to reach a steam spout port. The fins of the steam generator disclosed in Patent Literature 1 have a flat plate-shaped portion provided as extending horizontally for preventing running-up by the boiling water.